Skull-cutter.



IE'. HOLT.

SKULL GUTTER.. APPLIUATIQN FILED 11.13.14, 1910.

Patented Feb. 7, 1911.

'T'HE Nckms PETERS co', WASHINGTON, n. c.

FRANK I-IOIT, OF CHICAGO, ILLINOIS.

SKULL-CUTTER.

Specification of Letters Patent.

Patented Feb. 7, 1911.

Application filed March 14, 1910. Serial No. 549,306.

To all whom it may concern:

Be it known that I, FRANK I-IoLT, a citizen of the United States,residing in the city of Chicago, county of Cook, and State of Illinois,have invented a certain new and useful Improvement in Skull-Cutters, ofwhich the following is a specification.

The object of this invention is to provide a stronger and moreconvenient tool for the cutting of skulls in surgical operations thanhas been known before the invention thereof; and to protect the brainand the surrounding dura from injury in skull-cutting operations.

In the drawings Figure 1. is a side elevation of my device; Fig. 2. is alike elevation in section, in a plane coincident with the axis of thecutting tool, and Fig. 3 is a sectional elevation of my device at rightangles to that shown in Fig. 2, likewise coincident with the axis of thecutting tool.

Referring to the drawings, 4 represents the frame of my device, 5 ahandle, and 6 a thumbscrew by means of which the frame and handle arepivotally joined together.

7 designates a number of holes, all of the same diameter, drilledequi-distant from the axis of thumbscrew 6 into frame 4 and handle 5,respectively; and 8 a pin which is inserted into any two of holes 7, inframe 4 and handle 5, respectively, which are made to register byvarying the angle between frame 4 and handle 5. The purpose of theseholes 7 and pin 3 is to fix frame 4 and handle 5 more firmly inposition, at various angles to each other, than can be done by the meretightening of thumbserew 6. A bearing-tube 10 is fastened in the lowerend of frame 4 by setscrew 11. Milling tool 9 is held in bearing 10 byspring 12, fastened by screws 13 to frame 4, and engaging, withbent-over edge 36, circular groove 14 in milling tool 9. The foot ofthis milling tool is provided with axial extension 15 which is mountedin opening 1G drilled through shoe 17 which by means of shank 18 andset-screw 11 is firmly attached to frame 4. The top of tool 9 isprovided with slot 19 adapted for engagement to the operating end of aflexible shaft 20; and tube 21, integral with frame 4, surrounds the topof tool 9 for the purpose of holding shaft 20 in proper engagement withslot 19; such engagement being further secured by spring 22, attached tosaid tube 21 by screw 23, and adapted to engage with its bent-over edge24, projecting into the interior of tube 21 through opening 40 therein,circular groove 25 in shaft 20.

In vertical bearings 26 and 27, located in projections 23 and 29,respectively, which extend from the front end of, and are integral with,frame 4, is mounted, and adjustably held, by nut- 30 and locknut 31,vertical shaft 32, the upper end of which is threaded for engagementwith nut 30 and locknut 31, while into its lower end is fastened, madeintegral therewith, guard 33 the upper end of which projects sidewisefrom shaft 32 into vertical slot 34, to prevent turning, while its lowerend is formed into a loop which surrounds with ample latitude for slighthorizontal motion in any direction, shank 18 and the cutting portion ofmilling tool 9.

The operation of my device is as follows z-After a sufficient portion ofthe skull to be operated upon has been laid bare and a preliminaryopening made by means of a trephine, shoe 17 is inserted between theedge of the skull and the dura; then guard 33 is adjusted, by means ofturning nuts 30 and 31, so that the distance between the upper side ofshoe 17 and the lower side of loop 35 slightly exceeds the thickness ofthe skull. Milling tool 9 is thereupon made to rotate through powertransmitted by means of shaft 20, and thereupon is pushed against theedge of the skull with an intermittent motion, along the path desired.

One of the great dangers connected with the use of skull-cutting toolsas heretofore constructed, has been the absence of any practical andsu'liicient means for preventing a slipping of the cutting tool beyondits proper depth. This with my device is absolutely .prevented by guard33 with loop 35, which can readily be adjusted to the thickness of anyskull. by nut 30 and locknut 31. Another great advantage is the use ofhandle 5 and its adjustability to different angles by means of the jointbetween it and frame 4. Previous tools had no such handle and theoperators grasp was not firm enough, and his view constantly obstructedby his hand.

I claim- 1. In skull-cutting tools, the combination of a frame, a rotarycutting tool, means to rotate the tool, a guard to prevent contact ofthe cutting tool with the dura, and

anotherV guard to prevent slipping of the tool beyond its proper depth.

2. In skull-cutting tools, the combination4 of a frame, a rotary cuttingtool, means to rotate the tool, a guard in Which the lower end of the`euttingtool is mounted, and a loop-formed guard surrounding the Cuttingtool above and adjustable With reference to, the first-named guard.

3. In skull-cutting tools, the combination of a rotary cutting tool,means to rotate the tool, and a guard in Which the lower Yend of thecutting tool is mounted, Wit-b a frame carrying atits front end anadjustable guard for limiting the distance to which the tool shallextend below the upper surface of the skull, and at itsrear a handleadjustable to different angles with the cutting tool.

FRANK HOLT.

Vitnesses:

F. J. Bnsnnnn, Ror. A. KRoEBnR.

